Anion exchanges are generally prepared by quaternization of crosslinked chloromethylated polystyrene-DVB polymeric film. The synthesis of intermediate halomethylated (chloromethylated) polystyrene-DVB membranes involves the use of carcinogenic chloromethyl ether (CME). The use of CME for AEM preparation is hazardous to health.
The article “A novel positively charged composite membrane for nanofiltration prepared from poly (2,6-dimethyl-1,4-phenyleneoxide) by in situ amine crosslinking” published in J. Memb. Sci., 215, 25-32 (2003), by Tongwen et. al., describes the preparation of anion exchange resin from linear engineering plastics poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and its characterization. A base substrate made of aryl-brominated PPO polymers and a top layer made of benzyl- and aryl-brominated PPO polymers are taken together and subjected to in-situ amine crosslinking to obtain a membrane. The resultant membrane was characterized with pure water flux and rejection of electrolytes MgCl2 and NaCl. The properties of the nanofiltration membrane are significantly affected by the type of brominated polymers of the top layer, the amination time, and the composition of amination medium.
The article “Anion Exchange Membranes by Bromination of Benzylmethyl-Containing Poly(sulfone)s”, published in Macromolecules, 43, 2349-2356, (2010), by Jingling Yan and Michael A. Hickner, discloses the properties of anion-conducting membranes synthesized by halomethylation and quaternization of benzylmethyl-containing poly(sulfone)s. The benzylmethyl moieties serve as precursors to cationic sites, are introduced during polymer synthesis, thereby circumventing post modification of the polymer by chloromethylation.
The article entitled “Fundamental studies of a new series of anion exchange membranes: Membranes prepared from bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) and pyridine”, published in Journal of Membrane Science 279 (2006) 200-208, by Ming Gong et. al., describes how anion exchange membranes containing pyridinium groups were prepared by quaternization of bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) membrane with pyridine. The prepared. AEM showed relatively low IEC, high water content and low membrane potential, which was due to the erosion of pyridine during the amination reaction.
Reference may be made to an article by Blanc, G. L., published in Bull. Soc. Chin., France, 33, 313, (1923), wherein they disclosed that the halomethylated aromatic hydrocarbons and polymeric analogues are promising key intermediate for the synthesis of many valuable chemicals for targeted applications for both laboratory and industrial scale. The halomethylation reaction particularly, Lewis acid catalyzed chloromethylation of aromatic group is an important intermediates step in realizing polymeric materials.
The article entitled “Porogenic Solvents Influence on Morphology of 4-Vinylbenzyl Chloride Based PolyHIPEs”, published in Macromolcules, 41, 3543-3546 (2008), by Peter Krajnc et. al., describes how the poly(high internal phase emulsion) materials were prepared from concentrated emulsions containing 4-vinylbenzyl chloride as the reactive monomer and divinylbenzene as the cross-linker. The process of drying the polyHIPE materials also influenced the wet porosity. They have not attempted directly from methyl vinyl benzene.
The article entitled “A New Strategy to Microporous Polymers: Knitting Rigid Aromatic Building Blocks by External Cross-Linker”, published in Macromolcules, 44, 2410-2414 (2011), by Bien Tan et. al. They describe a series of microporous polymers via a low-cost versatile strategy, which involves “knitting” rigid aromatic building blocks, such as benzene, biphenyl, 1,3,5-triphenylbenzene, methylbenzene, chlorobenzene, and phenol using an external cross-linker. These materials are predominantly microporous and exhibit high surface areas. Moreover, different building blocks can generate materials with different pore structures, functional groups and application properties, which are significant for materials design. They used dimethoxymethane as linkers instead of CME.